Simplify the following expression: ${2z+9(9z-4)}$
Solution: Distribute the ${9}$ into the parentheses: $ 2z + {9(}\gray{9z-4}{)} $ $ 2z + {81z-36} $ Combine the $z$ terms: $ {2z + 81z} - 36$ $ {83z} - 36$ The simplified expression is $83z-36$